1. Field of the Invention
The present invention relates to Ti-4 protein, which is a protein derived from salivary gland of Triatoma infestans (an assassin bug) exhibiting activity to inhibit platelet aggregation, and to a gene encoding the Ti-4 protein.
2. Description of the Related Art
With progression of aging of society, treatment of adult diseases as a social problem is becoming more important. What is the most important for the welfare of such aging society is treatment and prevention of symptoms related to adult diseases, particularly cardiovascular disorders resulting from vascular sclerosis such as hypertension, pulmonary hypertension, myocardial infarction, cerebral infarction, pulmonary infarction and vascular spasms followed by subarachnoid hemorrhage. Such vascular disorders can be prevented and treated by administration of vasodepressors, blood coagulation inhibitors and platelet aggregation inhibitors to the patients. The known peptide having an anticoagulant activity which may be used as a medicine for treating such vascular disorders includes hirudine, a peptide isolated from salivary gland of leech. Hirudine is an anticoagulant peptide isolated from salivary gland of assassin bugs and it exhibits anti-thrombic activity. Ti-4 protein of this invention and a gene encoding the protein are novel. However, general knowledge on physiologically active substances isolated from salivary glands of assassin bugs are described as reviews in the following scientific journals:    (1) Ribeiro, J. M., “Role of saliva in blood-feeding by arthropods”, Annu. Rev. Entomol., 1987, vol.32, p463-478    (2) Basanova, A. V., Baskova, I. P., and Zavalova, L. L., “Vascular-platelet and plasma hemostatis regulators from bloodsucking animals” Biochemistry, 2002, vol67, p143-150
However, hirudine has some problems when applied as a medicine, those are, synthesis of hirudine is difficult, and it has some adverse side-effects. To achieve large amount of production of the compound to be used as a medicine in safely, it is necessary to solve the above problems. Thus, isolation of a protein whose synthesis is easy and capable of inhibiting the aggregation of platelets without causing any notable side-effects has been needed. If such a protein were produced, it would be a useful lead compound in the production of an anticoagulant, and be highly promising in the development of new medicines.